For the Austrian governor of Lombardy and a collector of antiquities, Count Karl von Firmian, Cignaroli painted two canvases on Greco-Roman episodes, a thematic preferred by Neoclassic painters: Death of Cato (1759) and Death of Socrates.

Giambettino was born into a family of artists, and this tradition continued after his death with his children. Artists from his family who were contemporaries and elders of Giambettino include his uncle Leonardo Seniore, and his two sons (cousins of Giambettino), Martino and Pietro.[2]